Using the PIV method to design synthetic jet actuators and investigate non-steady-state jet flow

A synthetic jet is a high frequency unsteady flow created as a result of cyclic suction and blowing through an orifice.A time averaged analysis of the flow structure within a synthetic jet is of limited value.In view of this, time dependent local velocity measurements, using a hot wire anemometer, are reported for a synthetic jet with a rectangular orifice of aspect ratio 70.Detailed measurements of local flow velocity, in quiescent conditions, within a control volume in the jet production region above the orifice exit plane, are presented.These data are analysed synchronous with the synthetic jet excitation signal to aid understanding of the periodic nature of resulting jet structure.Instantaneous velocity profiles, normalized velocity time histories and, normalized power spectra are used to understand the flow development and cyclic characteristics.Emphasis is placed on the jet development between the orifice exit plane and the point at which it becomes a steady jet at nominally 20 slot widths above the orifice.